Sounds to me like your travel agent is getting more commissionfor sending you to Phuket! We went to Vietnam for the first time this year, having been to Thailand 5 times previously and I really don't know what she's talking about! Vietnam is certainly much cheaper than Thailand especially with the current exchange rates and surely you'd have to have two hotel rooms for 6 of you wherever in the world you went. You say you're not really looking for a relaxing holiday anyway and there's certainly plenty of adventure to be found in Vietnam. Personally, if I had to choose between north and south Vietnam, I'd go for south, but it may be worth looking at which part has the best weather conditions for the time of year you wish to travel.